What's a shark's "yummy hum"?

Had you spent much time in a cattle drive or wagon train in the United States, you may have become familiar with the concept of the dinner bell. In more refined and civilized quarters of the nation during the agrarian period of American history, dinner bells were actual bells (and usually ornate ones). But in the rough-and-tumble Western U.S., they were often simple metal triangles, hung from the chuck wagon and rung by men with nicknames like "Cookie." But regardless of how the dinner bell was shaped, when it rang it meant the same thing: Come and get it!

There's a long association between sound and hunger. Perhaps they're most famously linked by Ivan Pavlov's experiments. Pavlov was a Russian physiologist who conducted research into digestion during the 19th and 20th centuries. While he was most interested in physiology, he inadvertently uncovered the psychological phenomenon of conditioning.

Shark Quizzes

Pavlov experimented by ringing a metronome whenever he presented his dogs with food -- an instance when he knew his dogs would salivate. Over time, he rang the metronome without offering any food and found that his dogs still salivated. Pavlov was the first to prove that physical responses could be elicited by external stimuli. His work provided much of the framework for modern behavioral psychology [source: PBS].

So if humans have their dinner bells and Pavlov's dogs had their metronome, do other animals associate sounds with food? Possibly. There are some people who think that sharks in particular respond to something called a yummy hum. But what exactly is a yummy hum all about? Read the next page to find out.